Microwave Dielectric Properties of Fused Silica Prepared by Different Approaches

Fused silica was prepared by different approaches, and the microwave dielectric properties were investigated. For the fused silica sintered at 1100 degrees C by solid-state sintering, the dielectric constant (epsilon(r)) and Qf value increased with increasing the sintering time up to 5h, while the temperature coefficient of resonant frequency ((f)) decreased. The optimal properties with low epsilon(r) of 3.72, high Qf value of 44,300GHz, and low (f) of -14.4ppm/degrees C were achieved when sintered at 1100 degrees C for 5h. The microwave dielectric properties could be further improved by other preparing approaches, as listed below: epsilon(r)=3.90, Qf=63,500GHz, (f)=-5.7ppm/degrees C for spark plasma sintering, and epsilon(r)=3.83, Qf=122,100GHz, (f)=-8.3ppm/degrees C for melting method. The results showed that fused silica was a good candidate as a microwave substrate material.